The Golden Compass, the Hollywood adaptation of Philip Pullman's His Dark Materials trilogy, launched in Cannes yesterday with a sneak preview of the film, which will hit UK cinemas at Christmas.

Chris Weitz, its screenwriter and director, used the event to address speculation about whether the books' firmly anti-religious message would be retained.

Referring to the Magisterium - the all-powerful religious body that wields total political power in the world of Lyra, the heroine - he said: "In the books the Magisterium is a version of the Catholic church gone wildly astray from its roots. If that's what you want in the film, you'll be disappointed. We have expanded the range of meanings that the Magisterium represents."

He added that there would be no specific marketing to neutralise any potential religious backlash in the US. "We're going to let the film talk for itself," he said.

Speaking from his home in Oxford, Pullman told the Guardian: "The Magisterium as I conceived it always did stand for a range of things, including organised religion and secular authority.

"The outline of the story is faithful to what I wrote, given my knowledge of what they've done - and given they have compressed a story that takes 11 hours to read out into two hours or so."

Weitz said: "Philip Pullman is against any kind of organised dogma, whether it is church hierarchy or, say, a Soviet hierarchy. We often deal quite obliquely with it in the film ... but we have done service to Pullman's books. Those people who read them for their philosophical content will not be disappointed."

The unknown 13-year-old who plays Lyra made her first public appearance yesterday. Dakota Blue Richards, who lives in Brighton, was one of thousands of hopefuls who attended open auditions.

"We were not just casting an actor, we were also casting a family situation," said Weitz. "She had to handle the strain of acting and, when not acting, going to school. She had the hardest job. And it was not just hard for her, but for her mother, who had to make enormous sacrifices of time." Richards said she was already very familiar with Pullman's trilogy: "My mother read the books to me when I was about nine, and I saw the plays at the National Theatre. I thought if I could play any role, it would be Lyra. I have treated the experience as if I am in two different worlds, the normal life of being who I was before, and all this. I try not to let the film affect going to school, and being me."

A 20-minute preview showed the film's luxurious use of locations from All Souls College, Oxford, to Swiss glaciers, its impressive special effects, and a silky-looking performance from Nicole Kidman, who plays the evil-doing but ultimately vulnerable Mrs Coulter.

The cast also includes Daniel Craig as Lord Asriel, Eva Green (who played opposite Craig as Vesper Lynd in Casino Royale) as the witch Serafina Pekkala, Sam Elliott as Lee Scoresby, and Simon McBurney as Fra Pavel.